/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.math;

import static com.google.common.math.MathBenchmarking.ARRAY_MASK;
import static com.google.common.math.MathBenchmarking.ARRAY_SIZE;
import static com.google.common.math.MathBenchmarking.RANDOM_SOURCE;
import static com.google.common.math.MathBenchmarking.randomBigInteger;
import static com.google.common.math.MathBenchmarking.randomNonNegativeBigInteger;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;

/**
 * Benchmarks against the Apache Commons Math utilities.
 *
 * <p>
 * Note: the Apache benchmarks are not open sourced to avoid the extra dependency.
 *
 * @author Louis Wasserman
 */
public class ApacheBenchmark {
    private enum Impl {
        GUAVA {
            @Override
            public double factorialDouble(int n) {
                return DoubleMath.factorial(n);
            }

            @Override
            public int gcdInt(int a, int b) {
                return IntMath.gcd(a, b);
            }

            @Override
            public long gcdLong(long a, long b) {
                return LongMath.gcd(a, b);
            }

            @Override
            public long binomialCoefficient(int n, int k) {
                return LongMath.binomial(n, k);
            }

            @Override
            public boolean noAddOverflow(int a, int b) {
                try {
                    int unused = IntMath.checkedAdd(a, b);
                    return true;
                } catch (ArithmeticException e) {
                    return false;
                }
            }

            @Override
            public boolean noAddOverflow(long a, long b) {
                try {
                    long unused = LongMath.checkedAdd(a, b);
                    return true;
                } catch (ArithmeticException e) {
                    return false;
                }
            }

            @Override
            public boolean noMulOverflow(int a, int b) {
                try {
                    int unused = IntMath.checkedMultiply(a, b);
                    return true;
                } catch (ArithmeticException e) {
                    return false;
                }
            }

            @Override
            public boolean noMulOverflow(long a, long b) {
                try {
                    long unused = LongMath.checkedMultiply(a, b);
                    return true;
                } catch (ArithmeticException e) {
                    return false;
                }
            }
        };

        public abstract double factorialDouble(int n);

        public abstract long binomialCoefficient(int n, int k);

        public abstract int gcdInt(int a, int b);

        public abstract long gcdLong(long a, long b);

        public abstract boolean noAddOverflow(int a, int b);

        public abstract boolean noAddOverflow(long a, long b);

        public abstract boolean noMulOverflow(int a, int b);

        public abstract boolean noMulOverflow(long a, long b);
    }

    private final int[] factorials = new int[ARRAY_SIZE];
    private final int[][] binomials = new int[ARRAY_SIZE][2];
    private final int[][] nonnegInt = new int[ARRAY_SIZE][2];
    private final long[][] nonnegLong = new long[ARRAY_SIZE][2];
    private final int[][] intsToAdd = new int[ARRAY_SIZE][2];
    private final int[][] intsToMul = new int[ARRAY_SIZE][2];
    private final long[][] longsToAdd = new long[ARRAY_SIZE][2];
    private final long[][] longsToMul = new long[ARRAY_SIZE][2];

    @Param({"APACHE", "GUAVA"})
    Impl impl;

    @BeforeExperiment
    void setUp() {
        for (int i = 0; i < ARRAY_SIZE; i++) {
            factorials[i] = RANDOM_SOURCE.nextInt(200);
            for (int j = 0; j < 2; j++) {
                nonnegInt[i][j] = randomNonNegativeBigInteger(Integer.SIZE - 2).intValue();
                nonnegLong[i][j] = randomNonNegativeBigInteger(Long.SIZE - 2).longValue();
            }
            do {
                for (int j = 0; j < 2; j++) {
                    intsToAdd[i][j] = randomBigInteger(Integer.SIZE - 2).intValue();
                }
            } while (!Impl.GUAVA.noAddOverflow(intsToAdd[i][0], intsToAdd[i][1]));
            do {
                for (int j = 0; j < 2; j++) {
                    longsToAdd[i][j] = randomBigInteger(Long.SIZE - 2).longValue();
                }
            } while (!Impl.GUAVA.noAddOverflow(longsToAdd[i][0], longsToAdd[i][1]));
            do {
                for (int j = 0; j < 2; j++) {
                    intsToMul[i][j] = randomBigInteger(Integer.SIZE - 2).intValue();
                }
            } while (!Impl.GUAVA.noMulOverflow(intsToMul[i][0], intsToMul[i][1]));
            do {
                for (int j = 0; j < 2; j++) {
                    longsToMul[i][j] = randomBigInteger(Long.SIZE - 2).longValue();
                }
            } while (!Impl.GUAVA.noMulOverflow(longsToMul[i][0], longsToMul[i][1]));

            int k = binomials[i][1] = RANDOM_SOURCE.nextInt(MathBenchmarking.biggestBinomials.length);
            binomials[i][0] = RANDOM_SOURCE.nextInt(MathBenchmarking.biggestBinomials[k] - k) + k;
        }
    }

    @Benchmark
    long factorialDouble(int reps) {
        long tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            tmp += Double.doubleToRawLongBits(impl.factorialDouble(factorials[j]));
        }
        return tmp;
    }

    @Benchmark
    int intGCD(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            tmp += impl.gcdInt(nonnegInt[j][0], nonnegInt[j][1]);
        }
        return tmp;
    }

    @Benchmark
    long longGCD(int reps) {
        long tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            tmp += impl.gcdLong(nonnegLong[j][0], nonnegLong[j][1]);
        }
        return tmp;
    }

    @Benchmark
    long binomialCoefficient(int reps) {
        long tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            tmp += impl.binomialCoefficient(binomials[j][0], binomials[j][1]);
        }
        return tmp;
    }

    @Benchmark
    int intAddOverflow(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            if (impl.noAddOverflow(intsToAdd[j][0], intsToAdd[j][1])) {
                tmp++;
            }
        }
        return tmp;
    }

    @Benchmark
    int longAddOverflow(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            if (impl.noAddOverflow(longsToAdd[j][0], longsToAdd[j][1])) {
                tmp++;
            }
        }
        return tmp;
    }

    @Benchmark
    int intMulOverflow(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            if (impl.noMulOverflow(intsToMul[j][0], intsToMul[j][1])) {
                tmp++;
            }
        }
        return tmp;
    }

    @Benchmark
    int longMulOverflow(int reps) {
        int tmp = 0;
        for (int i = 0; i < reps; i++) {
            int j = i & ARRAY_MASK;
            if (impl.noMulOverflow(longsToMul[j][0], longsToMul[j][1])) {
                tmp++;
            }
        }
        return tmp;
    }
}
